The present invention relates to wireless telecommunications systems and, more particularly, to methods and apparatus monitoring network infrastructure performance by means of computer analysis of drive test results.
In a cellular radio communications system (wireless communications network), an area is divided geographically into a number of cell sites, each defined by a radio frequency (RF) radiation pattern from a respective base transceiver station (BTS) antenna. The BTS antennae in the cells are in turn coupled to a base station controller (BSC), which is then coupled to a telecommunications switch or other gateway, thereby facilitating communication with a telecommunications network such as the PSTN (public switched telephone network) or the Internet.
When a mobile station (such as a cellular telephone, pager, or appropriately equipped portable computer, for instance) is positioned in a cell, the mobile station communicates via an RF air interface with the BTS antenna of the cell. Consequently, a communication path is established between the mobile station and the telecommunications network, via the air interface, the BTS, and the gateway.
With the explosive growth in demand for wireless communications, network resources can be stressed. For instance, as the level of call traffic increases in a typical cell site, the likelihood of interference between mobile stations can increase substantially. In response to such an increase in call traffic, the base station of the cell may instruct all mobile stations in the cell to decrease their transmission power, and the base station may itself begin to communicate at a lower power level with each mobile station in the cell. With lower transmission power, however, call quality can diminish, and calls may ultimately be lost.
Further, as cities and landscapes evolve, changes to topography can substantially effect the operation of a wireless network. For instance, as buildings and trees rise or fall in or around a cell site, the radiation pattern of the cell site may change drastically. As a result of new or changed signal reflections, for instance, the signal-to-noise ratio in or around the cell site may become unacceptably low and calls may be dropped.
To help manage the call traffic in congested or evolving areas and in other circumstances, a service provider may make changes to the network, such as by repositioning cell sites, subdividing cell sites into a number of sectors, adding new cell sites, or reallocating frequencies among various coverage areas. However, in order to effectively decide when and where such changes should be made, and to otherwise provide subscribers with acceptable and expected quality of service, a need has arisen to monitor communication resources.
One way to monitor communication resources is to send technicians out into the field (i.e., into cell sites) with mobile diagnostic measurement (MDM) tools, to collect diagnostic data about network conditions. Once the data is collected, the data can be analyzed, and determinations can then be made about the state of the network and about what changes if any may be required. MDM tools are known and commercially available from companies such as ZK Celltest, Willtech (now Xcellon), Ericsson, and Agilent.
One such MDM tool may comprise a combination of a computer and one or more mobile stations connected to the computer via suitable cable connections. The computer can be programmed to send one or more instructions to the mobile stations via the cable connection, so as to cause the mobile station to take various actions and to report various parameter values to the computer. For instance, the computer may instruct the mobile station to initiate a number of phone calls or data sessions and, for each call/session, to report to the computer (i) the channel (frequency) used, (ii) the transmit power used, and (iii) an indication of whether the call/session succeeded or was dropped.
Conveniently, the MDM tool may be carried in a vehicle such as a car, so that measurements can be made at various geographic locations. One technician may drive the vehicle around town, while another technician in the vehicle can operate the MDM tool so as to record information about the network. Alternatively, the MDM tool can simply be carried in the trunk of the vehicle or elsewhere in or on the vehicle and can automatically collect information about the network. Ideally, the MDM tool would further include a GPS receiver adapted to collect location data points indicative of where the MDM tool made its measurements. The MDM tool could thus establish a log file that includes records each indicating measured network conditions and a corresponding geographic location. Further, the log file can include an MDM identifier that identifies the MDM tool that collected the data.
In a typical arrangement, the data collected by the MDM tool will then be transferred to a central reporting office, where the service provider can process the data and endeavor to make decisions about system resources. In this regard, the data could be transferred on disk or over a cable or network connection from the MDM tool to the central reporting office. Alternatively, in a preferred arrangement, the MDM tool can wirelessly report the test results to the central office, via a wireless packet data connection (e.g., via FTP) for instance.
The process of driving or otherwise conveying an MDM tool around a given geographic area to collect network information is known as “drive testing.” Conveniently, a wireless carrier can arrange with a trucking company, taxicab company, public transportation company, or other carrier to mount MDM tools in various vehicles so as to collect network information from throughout a desired area as those vehicles drive along their routes, which are referred to as “drive test routes.”
Background prior art references disclosing the state of the art in analysis of cell coverage in wireless networks and strategies for drive test routes include the following patents, each of which is incorporated by reference herein: Sanders et al., U.S. Pat. No. 6,754,487; Arpee et al., U.S. Pat. No. 6,711,404; Somoza, U.S. Pat. No. 6,336,035; Arpee et al., U.S. Pat. No. 6,606,494; Bemadin et al., U.S. Pat. No. 6,006,095; Rappaport et al., U.S. Pat. No. 5,451,839; Gutowski, U.S. Patent Application Publication US 2002/0063656; and Jensen, U.S. Patent Application publication US 2002/0009992.
There is a need in the art to more intelligently and efficiently plan drive test routes, for example so that a minimum of drive test units are needed to adequately measure system performance in a defined geographical market. The present invention meets that need by providing methods and systems for automated analysis of drive test data. The drive test data is analyzed in conjunction with geographical data such as population distribution, geographical data as to wireless device usage, and other factors with the aid of a computing system. The results of the analysis are made available for use by a human operator, such as a manager overseeing the drive test routes in a particular region, so as to enable the operator to revise drive test routes, or select new routes, that provide improved measurement data for the wireless network.